<!-- 
    node.removeChild(child):从DOM中删除一个子节点，返回删除的节点
    node是父节点(也就是父元素)

 -->
<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <button>删除</button>
    <ul>
        <li>熊大</li>
        <li>熊二</li>
        <li>光头强</li>
    </ul>

    <script>
        var btn = document.querySelector('button');
        var ul = document.querySelector('ul');

        //删除元素 //删除ul里面的第一个孩子
        ul.removeChild(ul.children[0]);
        btn.onclick = function () {
            //如果里面没有小li了，就禁用删除按钮
            if (ul.children.length == 0) {
                this.disabled = "true";   //this指的是当前按钮这个对象
            } else {
                ul.removeChild(ul.children[0]);
            }

        }
    </script>
</body>

</html>